The present invention relates to an organic electro-luminescence (EL) display driving system and a mobile communication terminal used this system.
As a display of a mobile communication terminal, mainly a liquid crystal display (LCD) has been used. However, the LCD has several problems. For example, the LCD needs a backlight, and its viewing angle from a user is narrow, and it is not suitable to display moving images, because its response speed is slow. On the other hand, an organic EL display does not need the backlight, because it emits light spontaneously, and its viewing angle from a user is wide, and it is suitable to display moving images, because its response speed is fast. Therefore, this organic EL display has been focused on.
However, in case that the organic EL display is used as the display of the mobile communication terminal, the organic EL display needs a far higher voltage than a voltage being currently used at the mobile communication terminal. Consequently, this high voltage is obtained by using a step-up type DC/DC converter. And as mentioned above, the organic EL display is a spontaneous light emitting element, and when displaying contents on the organic EL display are viewed under intense outside light, the displaying contents on the organic EL display must be displayed with high brightness. As a result, a large amount of electric power needs to be supplied to the mobile communication terminal. However, at the mobile communication terminal, the power is supplied from a power source whose capacity is limited, such as from a battery, consequently, when its power consumption becomes large, there is a problem that the time, which the mobile communication terminal can be used, becomes short.
It is therefore an object of the present invention to provide an organic EL display driving system and a mobile communication terminal used this system, in which the electric power consuming by the organic EL display can be reduced without damaging the visuality of displaying contents.
According to a first aspect of the present invention, for achieving the object mentioned above, there is provided an organic electro-luminescence (EL) display driving system. The organic EL display driving system provides a measuring means that measures the amount of incident light to an organic EL display, which emits light spontaneously, from the outside, and a power supply voltage controlling means that controls the power supply voltage for the organic EL display so that the power supply voltage is increased when the amount of the incident light is large, and the power supply voltage is decreased when the amount of the incident light is small.
According to a second aspect of the present invention, in the first aspect, the power supply voltage controlling means changes the power supply voltage for the organic EL display in proportion to the amount of the incident light.
According to a third aspect of the present invention, in the second aspect, the organic EL display driving system further provides a means which a user changes a proportional constant between the amount of the incident light and the power supply voltage for the organic EL display by an operation of the user.
According to a fourth aspect of the present invention, in the first aspect, the organic EL display driving system further provides a means for changing the offset of the power supply voltage corresponding to an operation by a user.
According to a fifth aspect of the present invention, in the first aspect, the organic EL display driving system further provides a means for changing the power supply voltage for the organic EL display by an operation of a user, regardless of the power supply voltage decided by the power supply controlling means.
According to a sixth aspect of the present invention, there is provided a mobile communication terminal. The mobile communication terminal provides the organic EL display driving system mentioned above.